A picture size conversion method (and device) is provided to avoid deterioration of picture display quality such as a blur and distortion, especially with respect to motion pictures which are displayed in accordance with an interlaced display method. Herein, a size conversion table storing display flags is created in accordance with a reduction ratio, wherein each of the display flags represents a decision whether to allow display with respect to each of horizontal lines. At first, the method discriminates whether the reduction ratio (R) belongs to a first range (0<R<½) or a second range (½≦R<1), while the method also discriminates whether each of horizontal lines belongs to an even-numbered field or an odd-numbered field within one frame. In the case of the first range of the reduction ratio, the method thins out all of horizontal lines belonging to the even-numbered field while selectively thinning out horizontal lines belonging to the odd-numbered field with reference to the size conversion table. In the case of the second range of the reduction ratio, the method does not at all thin out the horizontal lines of the even-numbered field while selectively thinning out the horizontal lines of the odd-numbered field with reference to the size conversion table. Thus, original pictures can be converted (or reduced) in sizes in different ways in response to the first range and second range of the reduction ratio respectively.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A picture size conversion device comprising: original picture storing means for storing one frame of original picture which is configured by an odd-numbered field and an even-numbered field; converted picture storing means; conversion table means for determining whether to thin out each of horizontal lines with respect to either the odd-numbered filed or the even-numbered field in accordance with a reduction ratio; and picture conversion means for with reference to the conversion table means, making a decision as to whether each of the horizontal lines of original picture data stored in the original picture storing means is thinned out or not, so that if the horizontal line is not thinned out, the picture conversion means reads from the original picture storing means original picture data corresponding to the horizontal line, which is then stored in the converted picture storing means.
2. A picture size conversion device according to claim 1 further comprising conversion table creation means for creating the conversion table means.
3. A picture size conversion device according to claim 2 , wherein the conversion table creation means creates the conversion table means in such a way that if the reduction ratio is greater than 0 and is less than , all of horizontal lines corresponding to one field, which is either the odd-numbered field and the even-numbered field, are thinned out while horizontal lines corresponding to another field are selectively thinned out in accordance with the reduction ratio.
4. A picture size conversion device according to claim 2 , wherein if the reduction ratio is or more but is less than 1, the conversion table creation means creates the conversion table means in such a way that horizontal lines corresponding to one field, which is either the odd-numbered field and the even-numbered field, are not at all thinned out while horizontal lines corresponding to another field are selectively thinned out in accordance with the reduction ratio.
5. A picture size conversion device according to claim 4 further comprising correction position table means for determining whether to perform filter process with respect to each of the horizontal lines of the original picture data, wherein the picture conversion means reads each of the horizontal lines of one of the odd-numbered field and the even-numbered field which are not at all thinned out from the original picture storing means so as to make a decision as to whether the filter process is required for each of the read horizontal lines or not with reference to the correction position table means, so that if the filter process is not required, the picture conversion means stores picture data of the read horizontal line which does not require the filter process in the converted picture storing means, while if the filter process is required, the picture conversion means performs the filter process on the read horizontal line which requires the filter process based on at least one of upper and lower horizontal lines which are located above and below the read horizontal line.
6. A picture size conversion device according to claim 5 further comprising correction position table creation means for creating the correction position table means on the basis of a result of a decision as to whether each of the upper and lower horizontal lines, within the horizontal lines of one of the odd-numbered field and the even-numbered field which are not thinned out, belong to a same field.
7. A picture size conversion device according to claim 2 , wherein when a converted picture size is designated, the conversion table creation means calculates the reduction ratio based on a picture display size of the original picture.
8. A picture size conversion device according to claim 2 further comprising: odd-numbered field decode means for extracting picture data of the odd-numbered field from original picture signals so as to store the extracted picture data in the original picture storing means; and even-numbered field decode means for extracting picture data of the even-numbered field from the original picture signals so as to store the extracted picture data in the original picture storing means.
9. A picture size conversion method comprising the steps of: determining whether to thin out each of horizontal lines of original picture data with reference to a conversion table designating horizontal lines which are thinned out, wherein in one of an odd-numbered field and an even-numbered field, each of horizontal lines which are selectively thinned out in accordance with a reduction ratio is determined in advance; and converting the original picture data to converted picture data in such a way that the horizontal line which is determined to be thinned out is thinned out while the horizontal line which is determined not to be thinned out is stored in converted picture storing means.
10. A picture size conversion method according to claim 9 further comprising the step of: creating the conversion table based on the reduction ratio.
11. A picture size conversion method according to claim 10 further comprising the steps of: if the reduction ratio is greater than 0 and is less than , thinning out all of the horizontal lines of the original picture data with respect to one field which is either the odd-numbered field or the even-numbered field; and converting the original picture data to the converted picture data in such a way that each of the horizontal lines of another field which are not thinned out is stored in the converted picture storing means.
12. A picture size conversion method according to claim 10 further comprising the step of: if the reduction ratio is or more but is less than 1, converting the original picture data to the converted picture data in such a way that all of the horizontal lines of the original picture data of one field, which is either the odd-numbered field or the even-numbered field, are not thinned out while each of the horizontal lines of another field which are not thinned out is stored in the converted picture storing means.
13. A picture size conversion method according to claim 12 further comprising the steps of: making a decision as to whether filter process is required with respect to each of the horizontal lines which are not thinned out or not with reference to a correction position table; storing the horizontal line which is not thinned out and for which the filter process is not required in the converted picture storing means; and performing the filter process on the horizontal line which is not thinned out and for which the filter process is required on the basis of one of upper and lower horizontal lines which are located above and below the horizontal line.
14. A picture size conversion method that performs picture size conversion on original pictures configured by frames each consisting of a first field and a second field in accordance with an interlaced display method, said picture size conversion method comprising the steps of: creating a size conversion table in accordance with a reduction ratio which is designated in advance, wherein the size conversion table stores display flags each representing a decision whether to allow display of each of horizontal lines; discriminating whether the reduction ratio belongs to a first range or a second range that is greater than the first range; discriminating whether a horizontal line that is presently processed belongs to the first field or the second field; thinning out the horizontal line that belongs to the first field if the reduction ratio belongs to the first range; and making a decision whether to thin out the horizontal line that belongs to the second field with reference to the size conversion table, whereby the original pictures are reduced in sizes in different ways in response to the first range and the second range of the reduction ratio respectively.
15. A picture size conversion method according to claim 14 , wherein the first range designates that the reduction ratio is less than while the second range designates that the reduction ratio is less than 1.
16. A picture size conversion method according to claim 14 , wherein the first field corresponds to an even-numbered field while the second field corresponds to an odd-numbered field.
17. A picture size conversion method according to claim 14 , wherein the horizontal line that belongs to the first field is not thinned out.
18. A picture size conversion method according to claim 14 further comprising the steps of: creating a correction position table in accordance with the reduction ratio, wherein the correction position table stores correction flags each representing a decision whether to perform correction with respect to a horizontal line that belongs to the second field and that is not thinned out; and performing filter process as the correction on the horizontal line.
19. A picture size conversion device according to claim 3 , wherein if the reduction ratio is or more but is less than 1, the conversion table creation means creates the conversion table means in such a way that horizontal lines corresponding to one field, which is either the odd-numbered field and the even-numbered field, are not at all thinned out while horizontal lines corresponding to another field are selectively thinned out in accordance with the reduction ratio.
20. A picture size conversion device according to claim 3 , wherein a converted picture size is designated, the conversion table creation means calculates the reduction ratio based on a picture display size of the original picture.
21. A picture size conversion device according to claim 4 , wherein a converted picture size is designated, the conversion table creation means calculates the reduction ratio based on a picture display size of the original picture.
22. A picture size conversion device according to claim 5 , wherein a converted picture size is designated, the conversion table creation means calculates the reduction ratio based on a picture display size of the original picture.
23. A picture size conversion device according to claim 6 , wherein a converted picture size is designated, the conversion table creation means calculates the reduction ratio based on a picture display size of the original picture.
24. A picture size conversion device according to claim 3 , further comprising: odd-numbered field decode means for extracting picture data of the odd-numbered field from original picture signals so as to store the extracted picture data in the original picture storing means; and even-numbered field decode means for extracting picture data of the even-numbered field from the original picture signals so as to store the extracted picture data in the original picture storing means.
25. A picture size conversion device according to claim 4 , further comprising: odd-numbered field decode means for extracting picture data of the odd-numbered field from original picture signals so as to store the extracted picture data in the original picture storing means; and even-numbered field decode means for extracting picture data of the even-numbered field from the original picture signals so as to store the extracted picture data in the original picture storing means.
26. A picture size conversion device according to claim 5 , further comprising: odd-numbered field decode means for extracting picture data of the odd-numbered field from original picture signals so as to store the extracted picture data in the original picture storing means; and even-numbered field decode means for extracting picture data of the even-numbered field from the original picture signals so as to store the extracted picture data in the original picture storing means.
27. A picture size conversion device according to claim 6 , further comprising: odd-numbered field decode means for extracting picture data of the odd-numbered field from original picture signals so as to store the extracted picture data in the original picture storing means; and even-numbered field decode means for extracting picture data of the even-numbered field from the original picture signals so as to store the extracted picture data in the original picture storing means.
28. A picture size conversion method according to claim 11 , further comprising the step of: if the reduction ratio is or more but is less than 1, converting the original picture data to the converted picture data in such a way that all of the horizontal lines of the original picture data of one field, which is either the odd-numbered field or the even-numbered field, are not thinned out while each of the horizontal lines of another field which are not thinned out is stored in the converted picture storing means.
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December 2, 1998
July 9, 2002
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